Mobile virtual network operators are sprouting up like crazy all over the U.S. after becoming nearly extinct a few years ago. Why the renaissance? According to two of those new virtual operators, GSM Nation and TIng, the big carriers are finally letting MVNOs spread their wings. Virtual operators are sprouting up like weeds in a garden – except these weeds are starting to look a lot more attractive than the rose beds they’re enveloping. These mobile virtual network operators (MVNOs) essentially resell the voice and data services of big operators, but often at much lower prices and with more flexible plans. In just the last few weeks we’ve seen several new ones pop up. Last Friday, GSM Nation gave us a sneak peak at the MVNO it plans to birth this fall, distinguishing itself from the pack with a retail portal that sells almost any smartphone. Data-only operator Karma emerged last week, touting a unique social model for sharing bandwidth with the masses. Last month, Voyager Mobile launched offering two simple but comprehensive plans – one with data and one without. start an MVNO